As a type of rotary machine, a compressor provided with a rotor that rotates about an axis thereof and compresses a gas such as air, and a casing surrounding the rotor. This compressor employs an extraction structure for guiding a part of the gas compressed by the rotor to the outside of the compressor.
For example, Japanese Unexamined Patent Application, First Publication No. 2012-180749 discloses a compressor that employs such extraction structure. An extraction chamber that communicates with a main flow passage of the air (compressed air) and a pipe that guides the air in the extraction chamber to an outside of the compressor are formed in the casing of this compressor. The extraction chamber is an annular space centering around the rotor. Furthermore, the pipe extends radially outward from the extraction chamber with respect to the rotor.
In the compressor employing the extraction structure, the air, which is extracted to the interior of the extraction chamber from the main flow passage, flows so as to swirl in a circumferential direction with a rotation of the rotor.